1. Field
The present disclosure relates to a semiconductor phosphor nanoparticle and a light-emitting element including a semiconductor phosphor nanoparticle.
2. Description of the Related Art
Semiconductor nanoparticles are known to exhibit a quantum size effect when their size is reduced to about exciton Bohr radius. A quantum size effect is a phenomenon associated with a decrease in size of a substance in which electrons in the substance can no longer move freely and can only assume a specific energy value rather than an arbitrary value. It is also known that changes in the size of a semiconductor nanoparticle that confines electrons change the energy state of the electrons and that the wavelength of light generated from a semiconductor nanoparticle becomes shorter as the particle size decreases. Semiconductor nanoparticles that exhibit such a quantum size effect have been a subject of much focus for use as phosphors, and studies are being made thereon
Semiconductor nanoparticles have an average particle size of 100 nm or less and high surface activity, and thus aggregate easily. When semiconductor nanoparticles are used as phosphors, aggregation of semiconductor nanoparticles adversely affects luminous efficiency of phosphors. In order to suppress aggregation, a technique of modifying surfaces of semiconductor nanoparticles with a protective agent has been proposed.
Japanese Unexamined Patent Application Publication No. 2010-138367 discloses a technique of modifying nanoparticle surfaces with a modifying agent having a thiol group so as to obtain semiconductor phosphor nanoparticles with high water dispersibility.
In making a device by using semiconductor phosphor nanoparticles, modified semiconductor phosphor nanoparticles are encapsulated in a resin or glass. In the case where semiconductor phosphor nanoparticles are encapsulated in glass by using an organoalkoxysilane such as tetraethyl orthosilicate (TEOS) or encapsulated in a resin by using a polymer material, luminous efficiency of the semiconductor phosphor nanoparticles is decreased.
This is probably due to the following reason. After semiconductor phosphor nanoparticles are dispersed in an organoalkoxysilane, stress is generated by condensation reaction that occurs by vitrification of the organoalkoxysilane, and causes dissociation of bonds between thiol modifying groups and surfaces of phosphor nanoparticles, thereby inducing defects in the surfaces of semiconductor phosphor nanoparticles.